deps: bump zentinel-agent-protocol to 0.6

Pinned "0.5", which resolves to 0.5.13 while current releases are 0.6.x.
No source changes were needed.

Verified against 0.6.24 with cargo build, cargo fmt --check, clippy with
-D warnings, and the test suite.

Author: raffaelschneider

Cargo.toml

@@ -23,7 +23,7 @@ path = "src/main.rs"
 
 [dependencies]
 # Zentinel protocol
-zentinel-agent-protocol = "0.5"
+zentinel-agent-protocol = "0.6"
 zentinel-common = "0.5"
 
 # Async runtime